Field of the Invention
The present invention relates to a cosmetic composition containing 3-O-alkyl-L-ascorbic acid or a salt thereof, which composition is superior in solubilization stability, preservation stability and the sense of use.
Discussion of the Background
Pigmentation of skin, which is observed in black spot, freckle, dark skin and the like, is considered to be generally caused by overproduction of melanin pigment by melanin pigment-producing cells in the skin. To improve or prevent pigmentation due to overproduction of melanin pigment, cosmetics containing L-ascorbic acid or a salt thereof have conventionally been proposed.
However, L-ascorbic acid and a salt thereof have problems in stability over time, odor and the like, since they develop color over time and produce odor and the like. As brightening agents that improve these problems, ascorbic acid derivatives such as 3-O-alkyl-L-ascorbic acid (patent document 1) and the like have been proposed.
However, since water solubility of alkylether derivatives of ascorbic acid such as 3-O-alkyl-L-ascorbic acid and the like decreases markedly, it is difficult to produce transparent cosmetics containing an ascorbic acid derivative and capable of maintaining the solubilized state. Also, preservation stability, sense of use and odor thereof are not satisfactory yet.
With such background, patent document 2 proposes cosmetics superior in preservation stability and brightening action, by blending 3-O-alkyl-L-ascorbic acid and a component with a skin activating effect. However, preservation stability was evaluated based only on the maintenance of brightening activity (tyrosinase activity inhibition rate) as an index, and solubilization stability, sense of use and odor are not specifically described at all.
Also, patent document 3 proposes cosmetics containing 3-O-alkyl-L-ascorbic acid and an anti-inflammatory agent, and recites skin lotion containing 3-O-ethyl-L-ascorbic acid, glycyrrhetinic acid, and polyoxyethylene(20)sorbitan monolaurate as an example. While patent document 3 describes that the aforementioned skin lotion was stable after preservation at 40° C. for 3 months, it does not refer to the sense of use.